Yaesu FT DX 9000D - COMPUTER AIDED TRANSCEIVER, Руководство по эксплуатации

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Page 25 FT
DX
9000D O
PERATION
M
ANUAL
NTCH Switch
This button turns the main band (VFO-A) IF notch
filter on and off. When the IF notch filter is activated,
the LED inside the button will glow red. The Notch
Filter center frequency is adjusted via the NTCH
knob, described in the previous section.
Advice
H
The width of the notch may be set to either “Wide”
or “Narrow” via Menu item “RX DSP 082 IF-
NOTCH-WIDTH” in the RX DSP Menu Group.
Setting this selection to “Narrow” will provide a
very sharp notch, with minimal disturbance to the
incoming signal wave-form.
H
The tuning rate of the Notch Filter being rather
slow, it frequently is useful to use the Audio Scope
of the TFT (either the Audio Spectrum Scope or
the Waterfall display) to adjust the center fre-
quency of the IF Notch Filter. In the Waterfall
display mode, the notched area will appear more
white than the background screen, while on the
Audio Spectrum Scope screen the notched area
will appear as a “hole” in the noise.
DNF Switch
This button turns the main band (VFO-A) Digital
Notch Filter on and off. When the Digital Notch Fil-
ter is activated, the LED indicator will glow red. This
is an automatic circuit, and there is no adjustment knob
for the DNF.
R.FLT Switch
This button selects the bandwidth for the main band
(VFO-A) receiver's first IF Roofing Filter. Available
selections are 3 kHz, 6 kHz, 15 kHz, or Auto, and the
LED indicator will change according to the bandwidth
selected.
Advice
Because the roofing filter is in the first IF, the protec-
tion it provides against interference is quite signifi-
cant. When set to AUTO, the SSB bandwidth is 6 kHz,
while CW is 3 kHz and FM/RTTY are 15 kHz. On a
crowded SSB band, however, you may wish to select
the 3 kHz filter, for the maximum possible interfer-
ence rejection.
DNR Switch
This button turns the Main band (VFO-A) Digital
Noise Reduction circuit on and off. When the Digital
Noise Reduction is activated, the LED inside the but-
ton will glow umber. Adjustment of the Noise Reduc-
tion level is provided by the DNR knob, described
in the next section.
CONT DNR Knob
CONT Knob
The inner CONT knob selects the desired sub band
(VFO-B) CONTOUR filter response. The CONTOUR
filter is engaged via the CONT switch, described in
the next section.
DNR Knob
The outer DNR knob selects the optimum Main
Band (VFO-A) Digital Noise Reduction response. The
Noise Reduction circuit is engaged via the DNR
switch, described in section
above.
CONT Button
This button turns the sub band (VFO-B) CONTOUR
filter on and off. When the CONTOUR filter is acti-
vated, the LED inside the button will glow umber. Ad-
justment of the CONTOUR filter’s center frequency
is provided by the CONT knob, described in sec-
tion
above.
Quick Note
There are times, when you’re trying to remove inter-
ference with a sharp DSP filter, that the remaining sig-
nal has a somewhat unnatural sound. This is caused
by the cutting of some frequency components, leav-
ing other components in excess. The CONTOUR fil-
ter allows you (especially) to roll off certain frequency
components inside the remaining passband, but in a
smooth manner that helps restore a natural sound and/
or raise intelligibility.
Advice
H
The action of the CONTOUR filter (either null-
ing or peaking of frequency components as you
adjust the center frequency) may be adjusted via
Menu item “RX DSP 079 MAIN-CONTOUR-
WIDTH.” The adjustment range includes settings
of -15 dB (nulling) to +10 dB (peaking).
H
The Audio Spectrum Scope (including the Wa-
terfall displays) on the Oscilloscope page of the
TFT can be particularly useful when adjusting the
CONT control (see section above), as you
can observe the position of the null or peak in the
audio passband.
F
RONT
P
ANEL
C
ONTROLS